Dehydrated Culture Media

Dehydrated Culture Media products are formulated to supply the required nutrients to allow for the growth of microorganisms. Used in combination with a variety of selective agents and incubation conditions a wide range of specific organisms can be isolated. With careful raw material selection of the various media components E&O can ensure a consistent level of quality and performance. For each formulation the necessary ingredients are accurately weighed, combined and blended together to produce a homogenous powdered product.

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  • Bacteriological agar is extracted from several species of red algae, Gelidium spp. Bacteriological agar is a solidifying agent used in the preparation of microbiological culture media.This agar is suitable for all bacteriological purposes and has a low concentration of metal ions.A firm gel is obtained at working concentrations of 1.0 to 1.5%.  
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  • Brain-heart infusion solids is a dehydrated infusion of porcine brains and heart. This product can be used in preparing microbiological culture media providing nitrogen, vitamins, minerals and amino acids.  
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  • Lactalbumin hydrolysate is obtained through enzymatic hydrolysis of lactalbumin protein in milk whey. This product is rich in essential amino acids as well as providing a source of nitrogen, carbon and vitamins. It is commonly utilized in media for tissue culture and for the production of vaccines as well as being useful for bacterial and fermentation media.  
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  • Soy peptone is manufactured from the enzymatic hydrolysis of soybean. This product provides a good source of nitrogen, carbohydrates, and vitamins. It is recommended for use in microbiological media for the detection and isolation of a wide variety of bacteria and fungi.  
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  • Beef extract is sourced from bovine tissue and supports the nutritive needs of microorganisms. Providing a mixture of amino acids, peptides, minerals and vitamins this product is recommended for use in microbiological culture media for the examination of water, milk and other materials.  
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  • Malt extract is sourced from hydrolyzed vegetal protein. Due to the high concentration of carbohydrate malt extract is particularly suited for the cultivation of yeasts and moulds especially in contaminated dairy products. In microbiological culture media it provides a source of nutrients, protein, and carbon.  
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  • Meat peptone is sourced from hydrolyzed proteins of animal tissue. This peptone consists of soluble amino acids and peptides that provide readily available nitrogen and other essential growth factors. It is primarily used for the cultivation of fastidious and non-fastidious microorganisms in microbiological culture media.  
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  • Yeast extract is obtained from selected autolyzed Saccharomyces cerevisiae cells. This product can be used in preparing microbiological culture media providing readily available soluble vitamins (notably B-complexes), amino acids, peptides, and other essential growth factors. Yeast extract is observed as an animal free source and is therefore used extensively in many non-animal cell culture formulations.  
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  • Tryptone is obtained by pancreatic digestion of casein. Casein is the main protein of milk and is a rich source of amino acid and nitrogen. This product can be used in preparing microbiological culture media providing nitrogen, vitamins, minerals and amino acids. Due to the high tryptophan content in tryptone it can be used in detecting indole production.  
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  • Bacteriological peptone is an economical source of nutrients provided by a balanced mixture of meat peptones and tryptone.The growth requirements of most non fastidious organisms will be fulfilled by the range of amino acids, peptides and proteoses in this mixture.  
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  • Sheep Blood Agar Base has been developed to provide a nutrient rich medium compatible with sheep blood for the cultivation of many bacteria, especially fastidious Streptococcus spp., without affecting haemolytic reactions. Alternative culture mediums, such as Blood agar base No. 2, can results in mixed haemolytic reactions for some Streptococcus spp. This is thought to occur due to the trace amounts of fermentable carbohydrates in yeast extract and the physiological difference between sheep and horse blood. The tryptone, peptone, and yeast extract provide the required nitrogen, carbon and vitamins in the medium. Sodium chloride maintains the osmotic balance. Related Supplements : LS0008 Staph/Strep Selective Supplement
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  • This medium is for the growth of fastidious anaerobes, particularly Bacteroides spp. Fastidious anaerobe broth is also suitable for anaerobic blood culture. The peptone and yeast extract provides the required carbon, nitrogen and vitamins. Haemin, vitamin k and L-cysteine HCl are growth factors required by some anaerobes. Sodium thioglycollate and L-cysteine HCl reduce the Eh of the medium and the agar helps maintain the Eh. Resazurin is a redox indicator and sodium chloride maintains the osmotic balance. NB: For best results it is recommended that the medium be heated in a boiling water bath, with the cap loosened, and then allowed to cool, with the cap tightened, immediately before use. The cap must be replaced on the container immediately after inoculation.  
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  • Primary Membrane Lactose Glucuronide Agar (mLGA) is used for the differentiation and enumeration of Escherichia coli and other coliforms through a single membrane filtration technique. The peptone and yeast extract provide the required nitrogen, carbon and vitamins. Sodium pyruvate protects injured cells enhancing recovery and growth of coliforms. Sodium lauryl sulphate is a selective agent that inhibits Gram-positive organisms. Lactose is a fermentable carbohydrate and phenol red is a pH indicator. Lactose fermentation will result in yellow colonies. X-glucuronide is a chromogenic substrate which can be cleaved by the enzyme ß-glucuronidase present in E. coli. This results in a blue colony, but in combination with lactose fermentations colonies will appear green. NB: Prepared plates stored at 2–8°C may show formation of surface crystals which will disappear when plates are warmed to >20°C Related Supplements :
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  • Bacillus cereus agar (PEMBA) is used for the selective isolation and enumeration of Bacillus cereus in food samples. It is said to be particularly suitable for the detection of small numbers of Bacilluscereus particularly in the presence of other contaminating organisms. Bacillus cereus agar (PEMBA) is based on the formulation developed by Holbrook and Anderson. The peptone provides the required carbon, nitrogen and vitamins. Mannitol is a fermentable carbohydrate. Bromothymol blue is a pH indicator used to detect mannitol fermentation. Sodium chloride maintains the osmotic balance. Magnesium sulphate provides divalent cations and sulphate. Di-sodium hydrogen phosphate and potassium dihydrogen phosphate are buffering agents. Egg yolk emulsion (BM0140) must be added to this media to assess lecithinase production. Sodium pyruvate is present to improve egg yolk precipitation and enhance B. cereus sporulation. The medium is made selective by the inclusion of polymyxin B sulphate (LS1051).
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  • Charcoal agar is used for the cultivation of fastidious organisms, particularly Bordetella pertussis. Charcoal agar is prepared according to the formulation developed by Mishulow, Sharpe and Cohen. This medium is an efficient substitute for Bordet-Gengou agar in the production of B. pertussis vaccines and can be used as a maintenance medium for stock cultures of Bordetella spp. Beef extract and peptone provide the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance. Starch and charcoal help in absorbing toxic metabolites that are produced during growth of the organism. Nicotinic acid is an essential growth factor for the growth of Bordetella spp. The addition of cephalexin (LS0018) inhibits accompanying contamination in the samples. NB: This is a basic medium only and contains no additional supplement. If cephalexin is added, it should be noted, that although coliforms are inhibited by this medium, Pseudomonas aeruginosa and some fungi will grow. Related Supplements : LS0018 Bordetella Selective Supplement
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  • A selective medium for the isolation and detection of dermatophytic fungi originally developed by Taplin et al. Dermatophytes appear as fluffy colonies with reddening of the medium while other fungi cause the medium to become yellow due to acid production. Yeasts will also grow on this medium but are readily distinguished by their distinct white/creamy colonies and distinctive smell. Soy peptone provides the required carbon, nitrogen and vitamins. Glucose is a fermentable carbohydrate. The inclusion of phenol red assists in the differentiation between saprophytic and environmental fungi. Although the low pH (pH 5.5) of the medium inhibits most bacteria chloramphenicol and cycloheximide are often added to further reduce the risk when processing material that may be more heavily contaminated. NB: Prolonged incubation should be avoided as this may cause fungi other than dermatophytes to turn the medium red. Related Supplements : LS0050 Chloramphenicol Selective Supplement
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  • Mueller Hinton agar is used for antimicrobial susceptibility testing by the disk diffusion method as described by Bauer-Kirby. It has been approved as the definitive medium for this purpose by the European Committee on Anitmicrobial Susceptibility Testing (EUCAST). This formulation conforms to Clinical and Laboratory Standard Institute (CLSI). Beef extract and acid hydrolysate of casein provides the required nitrogen, carbon and vitamins in the medium. Starch absorbs any toxic metabolites produced. The medium contains low levels of thymidine and thymine and controlled levels of calcium and magnesium ions. The base medium can be supplemented with blood (5 – 10%). Nicotinamide adenine dinucleotide (NAD) may be added at 20 mg/L to make the medium suitable for use with more fastidious organisms such as Streptococcus pneumoniae and Haemophilus influenzae (LS0005). Related Supplements : LS0005 NAD Supplement (20mgs/L), Defibrinated Horse Blood
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  • Yeast extract agar is a nutrient rich medium for the cultivation of non-fastidious bacteria, yeasts and moulds. Recommended for the plate count of microorganisms in water and dairy products. The yeast extract and peptone acts as a source of nitrogen, amino acids, carbon and vitamins. Related Supplements : LS0019 Oxytetracycline Selective Supplement
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  • A modification of Christensen’s medium by Maslen this medium is generally used to detect rapid urease activity of Proteus spp. although it can be used to detect urease activity of other enterobacteriaceae including urease producing Salmonella spp. and Shigella spp. Unlike Christensen’s medium when used for the later purpose it is not necessary to increase the incubation time. The peptone provides the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. The disodium phosphate and potassium dihydrogen phosphate are buffers and sodium chloride maintains osmotic balance. Phenol red is a pH indicator. Related Supplements : BM3000 Urea 40% Solution
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  • A modification of Christensen’s medium by Maslen this medium is generally used to detect rapid urease activity of Proteus spp. It can also be used to detect urease activity of other enterobacteriaceae including urease producing Salmonella spp. and Shigella spp. When used for the latter purpose it is necessary to increase the incubation time to as long as 48 hours. The peptone provides the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. The potassium dihydrogen phosphate is a buffer and sodium chloride maintains osmotic balance. Phenol red is a pH indicator. Related Supplements : BM3000 Urea 40% Solution
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  • Triple sugar iron agar is used to differentiate between some of the enterobacteriacae on the basis of four reactions: fermentation of lactose, glucose and sucrose and the production of hydrogen sulphide. Beef extract, yeast extract and peptone provide the required nitrogen, carbon and vitamins. Lactose, sucrose and glucose are carbohydrates. Acid production from their fermentation is detected by the phenol red pH indictor. Sodium thiosulphate is reduced to hydrogen sulphide which is detected by the ferric citrate indicator. Sodium chloride maintains osmotic balance.  
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  • This medium is intended primarily for use in sterility testing of biological fluids that are turbid or viscous and is recommended in the United States Pharmacopoeia. It can be used for the cultivation of both aerobic and anaerobic organisms. The yeast extract, tryptone and glucose act as carbon, nitrogen and vitamin sources in this medium. The inclusion of sodium thioglycollate and L-cystine ensure anaerobiosis even for many of the more fastidious anaerobes and they also inactivate mercury and many other heavy metallic compounds. Resazurin is an oxidation-reduction indicator which turns pink when oxidised and is colourless when reduced. Sodium chloride maintains osmotic balance. Agar reduces oxygen diffusion into the medium. NB - For best results it is recommended that the medium be heated in a boiling water bath, with the cap loosened, and then allowed to cool, with the cap tightened, immediately before use. The cap must be replaced on the container immediately after inoculation.
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  • Recent developments in culture media have given rise to the use of chromogenic substrates as a means of differentiating bacteria particularly among the coliform group of organisms. This is one such medium and has been developed as a selective medium for the isolation and enumeration of Escherichia coli without the need for membranes or pre-incubation. Based on the formulation of Tryptone Bile Agar it incorporates a chromogenic substrate, X-Glucuronide, to detect the ß-glucuronidase enzyme which is specific for the majority of E. coli strains. Approximately, 3-4% of E. coli are glucuronidase negative including E. coli O157.(1) The advantage of the chromogenic substrate is that the reaction is concentrated within the colony resulting in distinctive blue/green colonies of E. coli while the other coliforms produce cream colonies. The tryptone provides the required carbon, nitrogen and vitamins. Bile salts No.3 is a selective agent against Gram-positive bacteria. X-glucuronide is a chromogenic substrate. Agar is solidifying agent.
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  • This medium was originally described by Slanetz and Bartley(1) for the enumeration of enterococci from water samples using membrane filtration. The medium has also become useful as a direct plating medium. Tryptose and yeast extract provide the required carbon, nitrogen and vitamins. Glucose is a fermentable carbohydrate. The di-potassium hydrogen phosphate acts as a buffer. Selectivity is achieved through the addition of sodium azide which is used to suppress the growth of Gram-negative organisms. The medium contains tetrazolium chloride, which is reduced by enterococci to the insoluble red dye formazan resulting in dark red colonies of enterococci on the agar. It should be noted that this reaction is not exclusive to enterococci and colonies should be confirmed by additional testing e.g. aesculin hydrolysis.